Switch from interfaces to abstract classes in dart:io.

runtime/bin/socket.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-interface ServerSocket default _ServerSocket {
+abstract class ServerSocket {
   /**
    * Constructs a new server socket, binds it to a given address and port,
    * and listens on it.
    */
-  ServerSocket(String bindAddress, int port, int backlog);
+  factory ServerSocket(String bindAddress, int port, int backlog) {
+    return new _ServerSocket(bindAddress, port, backlog);
+  }
 
   /**
    * The connection handler gets called when there is a new incoming
    * connection on the socket.
    */
   void set onConnection(void callback(Socket connection));
 
   /**
    * The error handler gets called when a socket error occurs.
    */
   void set onError(void callback(e));
 
   /**
    * Returns the port used by this socket.
    */
   int get port;
 
   /**
    * Closes the socket.
    */
   void close();
 }
 
 
-interface Socket extends Hashable default _Socket {
+abstract class Socket implements Hashable {
   /**
    * Constructs a new socket and initiate connecting it to the given
    * host on the given port. The returned socket is not yet connected
    * but ready for registration of callbacks.
    */
-  Socket(String host, int port);
+  factory Socket(String host, int port) => new _Socket(host, port);
 
   /**
    * Returns the number of received and non-read bytes in the socket that
    * can be read.
    */
   int available();
 
   /**
    * Reads up to [count] bytes of data from the socket and stores them into
    * buffer after buffer offset [offset]. The number of successfully read
@@ skipping 66 matching lines @@
    */
   String get remoteHost;
 
   /**
    * Closes the socket. Calling [close] will never throw an exception
    * and calling it several times is supported. If [halfClose] is true
    * the socket will only be closed for writing and it might still be
    * possible to read data. Calling [close] will not trigger a call to
    * [onClosed].
    */
-  void close([bool halfClose]);
+  void close([bool halfClose = false]);
 
   /**
    * Socket is hashable.
    */
   int hashCode();
 }
 
 
 class SocketIOException implements Exception {
   const SocketIOException([String this.message = "",
                            OSError this.osError = null]);
   String toString() {
     StringBuffer sb = new StringBuffer();
     sb.add("SocketIOException");
     if (!message.isEmpty()) {
       sb.add(": $message");
       if (osError != null) {
         sb.add(" ($osError)");
       }
     } else if (osError != null) {
       sb.add(": $osError");
     }
     return sb.toString();
   }
   final String message;
   final OSError osError;
 }